Thames Water has admitted businesses could be forced to leave the site in south Fulham from where it intends to build its controversial super sewer.

The utility firm needs an area the size of three football pitches - or 14,000 sqft - to accommodate a construction shaft, which is needed to mobilise equipment required to build the 20-mile long Thames Tunnel.

And it has been forced to admit its preferred sites, the neighbouring Hurlingham and Whiffen Wharfs, will have a huge impact on the ten firms which currently use next door Carnwath Business Park.

Construction, which could start in 2013 and take at least four years, will be extremely noisy and the firm acknowledges some business park operators may demand to leave.

A spokeswoman said: "If this site were to be used, we would look to work with the existing businesses to either reduce the impact on their day-to-day operations or, where this is not possible, we will look to help relocate them to an alternative site."

Hammersmith and Fulham Council has launched a concerted effort to stop the £3.6 billion tunnel, which will stop tons of raw sewage leaking into the river.

The authority believes the plans will destroy its ambitions to regenerate the wharfs, which are prime brownfield sites, and has made a number of claims to try and get Thames Water to change its mind.

It now accuses that the scheme would be in conflict with the National Grid, which allegedly already has plans to run cables linking its substations in Kensal Green and Wimbledon 20 metres beneath the wharfs.

Council leader Stephen Greenhalgh said: "Our worst super sewer fears are now being realised... The large sewer entry compound can only be justified in a large open area well away from existing homes and businesses.

"Thames Water needs to think seriously about the havoc their current plans will wreak and consider the alternatives before it is too late."

The authority also says a 'ventilation tower' needed at the site will pump out gases and noxious smells.

Thames Water says a final decision on the location of the construction site has not been reached.

"We are listening to everybody's feedback on every site and looking at potential alternative sites, which may be more suitable.

"The need for the scheme has all-party support, but the tricky bit is finding sites. There are no easy options.

"Our first phase of public consultation was the start, not the end, of a dialogue with potentially affected communities.

"We have not yet made any decisions on where the sites need to be and remain open to amending our original proposals, where possible."

A second, smaller construction site is planned at Hammersmith Embankment.

* Stephen Greenhalgh, MP Greg Hands, deputy mayor Kilt Malthouse and representatives from Thames Water will hold a public debate on the scheme at Hurlingham and Chelsea School on April 6 at 7.30pm.